Capacitive sensor devices according to the prior art are constructed as tubular capacitors or as plate capacitors.
German Utility Model Publication 19 27 694 (Bosch), published on Nov. 25, 1965, discloses an electrical capacitor with a folded sheet, tape or belt of insulating material carrying the capacitor plates or electrodes. The insulating material has metallized patterns that form the capacitor plates and conductor leads. The metallized patterns are all positioned on the same side of the tape or belt to permit a zig-zag folding pattern. Electrical connections are provided by metallized strips extending alongside the longitudinal edges of the tape or belt.
German Patent Publication DE 38 12 687 A1 (Normann et al.), published on Oct. 26, 1989 discloses a capacitive sensor for determining the filling level of a liquid in a container. Two electrodes 5 and 6 dip into the liquid. At least one of the two electrodes is provided with an electrically insulating cover layer. Two different frequencies are measured in order to ascertain the ohmic resistance and the capacitive resistance of the liquid between the electrodes. The respective signals are evaluated in a signal processing microcomputer for ascertaining the filling level as well as the water content in the liquid.
German Patent Publication DE 41 39 356 A1 (Brather), published on Jun. 3, 1993, discloses a plate capacitor for measuring of electric and dielectric characteristic values. Two covering electrodes (1) are spaced from each other. A central electrode (2) is positioned inside the space between the outer covering electrodes. The test samples to be measured are insertable into the spaces between the three electrodes.
Conventional measuring capacitors or capacitive sensors leave room for improvement especially with regard to their construction, more specifically, the ease of constructing and assemblying such capacitive sensors.